In the sprinkler fire extinguishing system of a high-rise building, a pressure regulating system having a pressure regulating valve and a pressure regulating pilot valve is provided to regulate the water pressure to be supplied to the sprinkler heads. By operation of the pressure regulating pilot valve, the interior of a secondary side of the pressure regulating valve is regulated to a steady pressure.
The degree of opening of a conventional pressure regulating valve is regulated by a spring urging the valve and a piston fixed thereto toward a closed position of the valve. The piston is fitted in a cylinder and the cylinder is connected to a secondary side of the pressure regulating pilot valve. As a result, the pressure regulating pilot valve causes the piston to slide together with the valve disk in accordance with changes in water pressure on the secondary side of the pressure regulating valve to vary the degree of opening of the pressure regulating valve.
The primary side of the pressure regulating pilot valve is connected to the primary side of the pressure regulating valve and the secondary side of the pressure regulating pilot valve is connected to the cylinder of the pressure regulating valve. Further, the valve disk of the pressure regulating pilot valve is connected to a shaft which is urged toward the open position of the valve. This shaft is connected to a diaphragm in an operation chamber and the operation chamber is in communication with the secondary side of the pressure regulating valve.
When water pressure of the secondary side of the pressure regulating valve is increased, the diaphragm in the operation chamber of the pressure regulating pilot valve is raised and the shaft is caused to slide toward the valve closing direction. When the secondary side water pressure of the pressure regulating valve is reduced, the diaphragm in the operation chamber of the pressure regulating pilot valve is lowered and the shaft is caused to slide toward the valve opening direction. The water pressure being supplied to the cylinder of the pressure regulating valve from the pressure regulating pilot valve is controlled by the sliding shaft.
In a sprinkler fire extinguishing system, water pressure may be abruptly increased for example at the time of starting a pump, or water pressure may be dropped for example due to the opening of a plurality of sprinkler heads. In a conventional pressure regulating valve, such forces are continuously applied on the main valve and it has been difficult to regulate the secondary pressure for a relatively wide range of the primary pressures. In other words, if the pressure on the primary side varies over a relatively wide range, forces acting upon the main valve due to the primary pressure vary when an attempt is made to maintain a certain degree of opening of the main valve is by the pressure regulating operation. Therefore the main vale is shifted from a predetermined degree of opening and the secondary pressure is shifted from a predetermined pressure.
Further, in a conventional pressure regulating pilot valve, if fluctuation occurs in the primary pressure, the degree of opening of the main valve is affected, since a large force acts upon one of the upper surface or the lower surface of the main valve. In other words, if the primary pressure changes when the pressure regulating valve is adjusting the degree of opening of the pressure regulating valve to regulate the secondary pressure, the degree of opening of the pressure regulating pilot valve is changed and the internal pressure of the cylinder of the pressure regulating valve is caused to change. As a result, the degree of opening of the pressure regulating valve changes and as result it is difficult to maintain the secondary pressure of the pressure regulating valve at a predetermined value.
Further, in the known prior art, a sealing force in the closed state of the valve is maintained by adjusting the elastic force of a spring which fuses the valve toward a closed position. However, while the sealing force is increased as the elastic force of the spring is increased, regulating operation on the degree of opening of the valve then becomes more difficult and a fine adjustment thereof becomes impossible. On the other hand, while regulation on the degree of opening of the valve becomes easier by reducing the force of the spring, it is more and more affected by a change in the primary side water pressure and there is a possibility of an undesirable opening of the valve. Thus, it is difficult to maintain a suitable sealing force by adjusting the elastic force of the spring.
In view of the above, it is an object of this invention to provide a pressure regulating system capable of operating steadily even when the primary pressure of the pressure regulating valve fluctuates.
Further, it is another object of the present invention to provide a pressure regulating system having a pressure regulating valve capable of providing a sufficient sealing force when the valve is closed.